This section provides background information related to the present disclosure which is not necessarily prior art.
Sensors are often used to detect electrical and chemical signals in biological tissue. For example, neural probes are used to detect electrical and chemical signals in brains, and to stimulate specific neurons or regions in brains. Recently, MicroElectroMechanical Systems (MEMS) are used to manufacture devices on a very small scale by micromachining. Although MEMS can be used to fabricate probes or sensors to be implanted in various biological tissues, the field of NeuroMEMS is now providing very small neural probes that may be implanted into brains. Micromachining neural probes using NeuroMEMS often includes depositing hard and rigid conductive materials rigid substrates.
Sensors and probes fabricated with electrically conductive materials that are hard and rigid due to a high Young's modulus are often not ideal for implanting into biological materials. For example, a stiffness mismatch between the hard and rigid electrically conductive material and brain tissue may cause negative tissue responses, irritation, and/or irreversible tissue damage. Stiffness mismatches are also problematic in regard to wearable sensors because a rigid material cannot have a conformal contact to skin, which causes deterioration or sensing performance over time.
Small and flexible probes and sensors are often advantageous over larger and rigid neural probes because, when implanted in brains for example, they result in less neural damage upon implantation and specific neurons may be targeted more closely. However, techniques used to fabricate small and flexible sensors and probes involve high temperatures and provide a low yield at a high cost. Therefore, there is a need to develop new flexible sensors at high yields and at a low cost.